The Highs and Lows of Caffeine
At least four out of five Americans regularly consume caffeine, the most widely used behaviorally active drug in the world. But does caffeine cause more than just a morning boost?
Over the years, caffeine has been singled out as a possible factor in heart disease , cancer, and birth defects, among others. Here's a look at why most experts say that moderate caffeine consumption is not a habit worth losing sleep over, and some advice for "addicts" who want to cut back.
They're the latest entry into the beverage market and may become the most potent way to get a caffeine fix. Dubbed "coffee colas," the carbonated, hybrid, coffee-flavored cola drinks have been test-marketed by the Pepsi-Cola Company and the Starbucks Coffee Company, while smaller beverage companies have put some right on the market. Only time will tell whether this latest caffeine twist will take off. But does the potential entry of another caffeine-containing concoction into the marketplace prove yet again that we're a nation of addicts?
In a manner of speaking, yes. Some 80% of Americans regularly consume caffeine, a drug that acts as a central nervous system stimulant. It increases heart rate, boosts urine production, and raises the metabolic rate (the speed at which the body burns calories to fuel necessary functions such as breathing). And as anyone who can't get going in the morning without a cup of coffee, tea, or a caffein-containing soft drink knows all too well, caffeine can be habit-forming.
While most experts say "addiction" is too strong a word to be used in conjunction with caffeine, researchers at Johns Hopkins University have identified a condition they call "caffeine dependence syndrome," characterized by at least three of the following four criteria:
- Withdrawal symptoms, such as headache, fatigue, and depression
- Caffeine consumption despite causing physical problems, such as irritating an ulcer
- Unsuccessful attempts to cut back on caffeine
- Tolerance to caffeine (for example, the ability to drink an extra cup of coffee and still fall asleep
Grounds for Kicking the Habit?
Although the idea of being "dependent" on caffeine is unsettling, most healthy people who drink a cup or two of coffee, tea, or soda every day suffer no more serious physical symptoms than jitteriness, irritability, and minor gastrointestinal upsets. Why, then, have scientists long suspected that caffeine might contribute to heart disease, cancer, birth defects, and other problems?
The snag here is that much of the early research linking caffeine to various conditions was clouded by a number of issues. When questioning people about their caffeine-consuming habits, for example, many researchers failed to ask about caffeine sources other than coffee or tea, such as soft drinks, chocolate, and certain medications (see chart).
In addition, most early studies neglected to account for differences in methods of preparing coffee. For example, some research has suggested that coffee drinking raises blood cholesterol levels. Yet most of that evidence comes from Scandinavia, where coffee is boiled rather than brewed.
Studies in the United States, on the other hand, have not come up with the same coffee-heart disease connection, presumably because coffee is brewed, which passes coffee through a filter. This process probably filters out certain chemical substances, which may be the cholesterol-raising culprits.
Another confounding issue is that even though caffeine and coffee drinking may not contribute to disease in and of themselves, they seem to go hand-in-hand with a lifestyle that does. One study conducted by researchers at the University of California, San Diego, found that coffee drinkers were more likely to smoke, drink alcohol, and eat high-fat diets than abstainers.So maybe it’s not the coffee, but rather the cream or cigarette accompanying the coffee that contributes to health problems.
Another report from a group of Boston-based researchers showed that compared to women who drank regular coffee, women who chose decaf were more likely to exercise and eat vegetables regularly.
Who Should Keep Caffeine in Check?
Some people would clearly do well to limit their caffeine consumption, or avoid it altogether. For example, people with ulcers or heartburn should stay away from caffeine because it stimulates the secretion of acid, which can irritate the lining of the gastrointestinal tract. (The chemicals in decaf coffee also boost acid secretion.)
Pregnant women should watch the amount of caffeine they consume as well. While moderate amounts (a cup or two of coffee a day) have not been proven to cause birth defects, caffeine does cross the placenta. Once caffeine enters the fetal bloodstream, large amounts can alter the unborn baby's normal heart rate and breathing. Some research also suggests that large amounts of caffeine may decrease bloodflow to the placenta, which in turn may raise the risk of miscarriage.
People with chronic headaches are strongly advised to quite all caffeinated products. Many headache specialists link caffeine intake with tension headaches.
On the other hand, there is some preliminary data that suggest caffeine intake my lower the risk of diabetes. Coffee may work by improving body’s sensitivity to insulin.
If You Decide to Quit . . .
Even if you only drink a cup or two of coffee, tea, or soda each day, try to cut back on caffeine gradually. Moderate caffeine users who stop cold turkey often suffer from withdrawal symptoms such as headaches, fatigue, moodiness, and nausea. Instead of switching over completely to decaffeinated coffee, substitute decaf for half your regular blend for a couple days and gradually wean yourself. Or, alternate decaf sodas with the regular version throughout the day until you feel comfortable weaning yourself from the caffeinated version completely.
A special note for smokers: Smokers need more caffeine to get a kick than their nonsmoking counterparts because smoking causes caffeine to be metabolized more quickly—one reason so many smokers get caught up in the coffee-and-cigarette habit. When a smoker kicks the cigarette habit, however, caffeine lingers in the bloodstream longer, which can add to the jitteriness and irritability that goes with giving up nicotine. To avoid frazzled nerves, smokers who quit cigarettes may want to cut back on caffeine at the same time
|Food and Beverages||
|Coffee and Tea|
|Coffee (6 oz cup), brewed||103|
|Coffee (6 oz cup), instant||57|
|Decaffeinated coffee (6 oz cup), brewed or instant||2|
|Tea (6 oz cup), brewed, black, steeped for 3 minutes||36|
|Instant iced tea (12 oz glass)||31|
|Mountain Dew, Mello Yello||52-54|
|Cocoa beverage (6 oz cup)||3-5|
|Chocolate milk beverage (8 oz carton)||5-8|
|Chocolate (1 oz)|
|Milk chocolate candy||7-18|
|Dark chocolate, semi-sweet||21|
|Chocolate flavored syrup||5|
|Arthritis Strength BC powder||36|
|Bayer Select maximum strength headache pain relief formula||130|
|Extra Strength Excedrin||130|
|Maximum Strength Arthriten||65|
|Maximum strength Multi Symptom Formula Midol||120|
Many manufacturers add caffeine to pain killers because it helps the drugs alleviate muscular aches and other discomforts more effectively. Some research also suggests that caffeine acts independently to relieve pain. The caffeine content of products may change, so contact the manufacturer for information on products you use frequently.
International Food Information Council
National Coffee Association of USA
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Oei SG, Vosters RP, van der Hagen NL. Fetal arrhythmia caused by excessive intake of caffeine by pregnant women. BMJ .1989;298:1075-1076.
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Strain EC, Mumford GK, Silverman K, Griffiths RR. Caffeine dependence syndrome. JAMA. 1994;272:1043-1048.
Willett WC, Stampfer MJ, Manson JE, et al. Coffee consumption and coronary heart disease in women: a ten-year follow-up. JAMA. 1996;275:458-462
Schwartz, BS, Stewart, WF, Simon D, Lipton, RB. Epidemiology of tension-type headache. JAMA. 1998;279:381-383.
Smith B, Wingard DL, Smith TC, Kritz-Silverstein D, Barrett-Connor E. Does coffee consumption reduce the risk of type 2 diabetes in individuals with impaired glucose? Diabetes Care. 2006;29(11):2385-2390.
Agardh EE, Carlsson S, Ahlbom A, et al. Coffee consumption, type 2 diabetes and impaired glucose tolerance in Swedish men and women. J Intern Med. 2004;255(6):645-652
Last reviewed February 2007 by Marcin Chwistek, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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